This is the fastest way to boost in halo reach.

Requirements:
3 Friends who also have a second account.
A mic to communicate with your partners.
2 Controllers.
2 Accounts with Xbox live gold.
Custom Challenges.

Custom Challenges needed:
Matchmaking Multiplayer > Kills > 500 Kills = 21,243cr.
Matchmaking Multiplayer > Medals > 750 Medals = 30,000cr.
Matchmaking Multiplayer > Wins > (any) wins = ???? (optional amount is all up to you)
For a total of 51,243cr. just from challenges. all challenges must be set at 3 hours.




How to do it.
First thing you will do is go to [ Register or Signin to view external links. ] and create your two custom challenges of 500 Kills and 750 Medals adding up to 51,243cr.

The next thing you will do is invite 3 other people to your game that also have second accounts and sign them all in.

The third thing you will do is start up grifball once in the game allow all second accounts to get 1 Kill in the first round and 1 Kill in the 5th round so you don't get caught or banned from earning credits for a week or two. Take turns killing the enemy team and switch every round decide what team goes first in the lobby you will get 10,000cr - 15,000cr for completing the game and 51,243cr so that would add up to an average of 66,243+ a game or two!.

information
You can NOT do this with a guest account because the challenge will only count what you and your guest have as kill like if you had 200 kills with your main account and your guest only had 2 kills only 2 kills would show up for the challenge but if you have 2 accounts in it will only count your main account which is what you want.

You can NOT get banned for this i have been doing it daily and hitting the daily credit cap in just a few games!. As long as everyone in the game has at least one kill they cant tell that you were boosting.

343 industries Does NOT reset ranks the most they can give you is a credit banned for a short amount of time.

The reason grifball is the recommended gametype is because you can get the most kills and you can get the most kills and every kill earns you a medal finishing both challenges at the same time. i also recommend using both hammer and sword to get all the spree medals for a little extra boost.

Once you "Turn-in" your challenge it will reward you all the Credits after the next game you play. you can also create challenges for Wins since both teams technically win because the score is 0 - 0.